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LCD-based method for evaluating modulation transfer function of optical lenses with poorly corrected distortion

OPTICAL ENGINEERING 2021年第6期60卷 063102-063102页

作者： He, Ping'an An, Xinlan Li, Xin Wuhan Univ Elect Informat Sch Wuhan Peoples R China

modulation transfer function (MTF) evaluation in the imaging of the optical lenses with poorly corrected geometric distortion involves sampling region of interest (ROI) images that are affected by geometric distortion, reducing its accuracy. A based liquid-crystal-device MTF (LMTF) method is proposed for this purpose by evaluating MTF of the medical rigid endoscope. This method establishes a mathematical model of geometric distortion and analyzes two sampling ROI image manners in MTF evaluation. Compared with the distortion factor (DF) manner, the distortion correction manner relaxes the value of the DF to twice the maximum non-distortion value, extends the sampling ROI image to twice the size, reduces the average R-RMSE value to 6%, and improves average accuracy on MTF by 1.2%. The experimental results provide good agreement with the theoretical prediction. Therefore, the proposed LMTF method can be referential for the other optical lenses with poorly corrected distortion. (C) The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License.

关键词： modulation transfer function medical rigid endoscope region of interest LMTF method distortion factor manner distortion correction manner

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modulation transfer function Characterization for GOES-16 Advanced Baseline Imager Using Lunar Observations 24

Modulation Transfer Function Characterization for GOES-16 Ad...

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Conference on Earth Observing Systems XXIV

作者： Wilson, Truman Xiong, Xiaoxiong Sci Syst & Applicat Inc 10210 Greenbelt Rd Lanham MD 20706 USA NASA GSFC Sci & Explorat Directorate Greenbelt MD 20771 USA

ISBN: (数字)9781510629486

ISBN: (纸本)9781510629486

GOES-16 is a geostationary satellite with a number of Earth- and Sun-observing instruments. Among these, the primary Earth-imaging instrument is the Advanced Baseline Imager (ABI), which contains 16 spectral bands that range in wavelength from 0.47 um to 13.3 um. In addition to Earth-observations, ABI also performs special data collects which observe the Moon for radiometric calibration validation and spatial characterization performance assessments. In this work, we use lunar images in order to calculate the modulation transfer function (MTF) of the optical systems of GOES-16 ABI for bands 1 - 6. The lunar limb against the dark background of space provides a good data set for performing a modified slanted-edge MTF calculation on-orbit. Using the location of the lunar day/night terminator, we select illuminated regions of the image near the lunar limb in both the North-South and East-West directions to calculate the MTF. For this work, we combine the edge profiles from successive lunar images on the same date in order to maximize the number of edge profiles used in the calculation. We also compare the MTF results for lunar observations throughout the GOES-16 mission to assess the stability of the MTF over time.

关键词： GOES-16 Advanced Baseline Imager modulation transfer function lunar calibration reflective solar bands

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Investigation of patch-based modulation transfer function (MTF) prediction framework in radiography

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RADIATION PHYSICS AND CHEMISTRY 2021年 189卷 109728-109728页

作者： Kim, Kyu Bom Jeong, Seong Ho Lee, Su Hwan Kim, Kyuseok Yonsei Univ Dept Integrat Med Digital Healthcare Coll Med Seoul South Korea Yonsei Univ Severance Hosp Div Pulm & Crit Care Med Dept Internal MedColl Med Seoul South Korea

The modulation transfer function (MTF) is a well-established in imaging systems and has played a significant role in assessing the performance of information transfer in accordance with the spatial frequency. Exist methods for measuring MTF require a pinhole, or a slit camera, an edge phantom, etc. These depend on the imaging system and exposure conditions. To overcome these problems, we investigated the proposed patch-based MTF prediction framework using a deep-learning algorithm in radiography. This proposed method directly allows for the predicted MTF from a single image without the need for additional devices and work. We used 800 to 1500 projections for supervised learning and selected many patches, including the edge information from input image for predicting the MTF, for which we used the Kendall's rank correlation. The quantitative evaluation performed included an intensity profile and a root-mean square error. In addition, we implemented the nonblind deblurring process to verify its image performance using the predicted MTF. Our methods successfully predicted the MTF and restored them from the degraded image without such artifacts as the ringing artifact that can occur when using the incorrect blur kernel. Consequently, the simulation and experimental results indicate that the proposed framework is useful to predicting the accurate MTF and is effective in improving radiographic image quality.

关键词： modulation transfer function Deep learning Rank correlation Deblurring Radiography

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Implementation, validation and application of a tool for the assessment of the modulation transfer function and noise power spectrum of dental CBCT scanners

Implementation, validation and application of a tool for the...

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Conference on Medical Imaging - Physics of Medical Imaging

作者： Merken, K. Zhang, G. Shaheen, E. Jacobs, R. Politis, C. Bosmans, H. Katholieke Univ Leuven Div Med Phys & Qual Assessment Dept Imaging & Pathol Leuven Belgium UZ Leuven Dept Radiol Leuven Belgium

ISBN: (纸本)9781510633926

Purpose: The aim of this study was to implement, validate and apply a tool for the assessment of the MTF and NPS of dental cone-beam CT (CBCT) scanners using up-to-date measurement methods tested earlier for multi-slice CT. Methods: Two cylindrical phantoms, compatible with small FOV CBCT scanning, were 3D printed. The MTF was calculated using the circular edge method, and the NPS as the 2D Fourier transform of homogeneous background ROIs. The influence of the phantom dimensions and the CNR on the MTF/NPS accuracy has been studied for a 10x10 cm(2) system FOV and corresponding voxel size of 0.25 mm(3). Validation for CBCT applications was set-up as follows: phantom images with known MTF/NPS were simulated, and from these images the MTF/NPS were calculated and the results compared to measurements. The tool was then applied on two very different CBCT systems. Results: For the MTF the minimum number of slices needed to achieve an error of at most 5 % could be fixed for several CNRs of the cylindrical insert (26 mm diameter). For the NPS, the number of 128x128 ROIs with an error of at most 5 % has been determined. Measurement results on two different dental CBCT scanners for a selection of imaging conditions are discussed. Conclusion: The study allowed to set guidelines for MTF and NPS calculations for dental CBCT. The first measurement experiments on the two systems did reveal some unexpected system characteristics, in which case more information from the manufacturers would be beneficial.

关键词： cone-beam computed tomography dental imaging image quality modulation transfer function noise power spectrum validation

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Characterization of anti-scatter grids via a modulation transfer function improvement factor using an edge device

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BIOMEDICAL PHYSICS & ENGINEERING EXPRESS 2021年第4期7卷 045001-045001页

作者： Maruyama, Sho Saito, Hiroki Shimosegawa, Masayuki Gunma Paz Univ Sch Radiol Sci Fac Hlth Sci Gunma Japan Gunma Prefectural Coll Hlth Sci Grad Sch Radiol Technol Gunma Japan

In optimizing the imaging conditions, changes in image quality due to scattered radiation are important evaluation targets. This study focuses on the evaluation of the image quality improvement characteristics obtained using anti-scatter grids in digital x-ray imaging, and proposes a frequency-dependent modulation transfer function (MTF) improvement factor, MIFG(u), as a new evaluation index. Accordingly, the purpose of this study is to clarify the validity and the usefulness of this proposed index in the performance evaluation of grids. The proposed MIFG(u) method is applied to evaluate several types of grids with different grid densities and ratios, and the characteristics of grids exhibiting different performances are examined. The proposed index is calculated based on the MTF measurement by using an edge test device. The results show that MIFG(u) changed according to grid type and scatter conditions. In particular, a remarkable difference was observed in the high scatter condition compared with the low condition. MIFG(u) in the vertical direction with regards to the absorbing strips shows a peak at 0.2-0.5 cycles/mm and be a constant value from approximately 1 cycle/mm;while MIFG(u) in the parallel direction is a constant value with respect to changes in spatial frequency. It is shown that MIFG(u) could be used to accurately describe the characteristics of a grid under different imaging conditions. We believe that the use of the proposed index could expand the options for optimizing imaging conditions when using grids.

关键词： anti-scatter grid modulation transfer function scattered radiation x-ray imaging

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Practical edge-based modulation transfer function measurement

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OPTICS EXPRESS 2019年第2期27卷 1345-1352页

作者： Masaoka, Kenichiro NHK Sci & Technol Res Labs Setagaya Ku 1-10-11 Kinuta Tokyo 1578510 Japan

The accuracy and precision of the modulation transfer function (MTF) of a sampled imaging system are affected by the shift-variant nature of subpixel binning of the pixel values in edge-based methods. This study demonstrates that a binning phase selected from a small number of binning phases can achieve a practical precision criterion for the MTF measurement. Furthermore, the new method proposed in this paper approximates the non-aliased, fundamental MTF without edge angle estimation and the following subpixel binning. The algorithm simply averages the aliased MTFs calculated from the row-by-row edge gradients in the region of a bitonal edge image and removes an assumed aliasing component. This method is also applicable to an oblique and non-straight edge. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

关键词： Digital image processing Discrete Fourier transforms Fourier transforms modulation transfer function Phase shift Spatial frequency

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Experimental demonstration of wave-front coded imaging with a very low response of the modulation transfer function at the Nyquist frequency

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APPLIED OPTICS 2019年第35期58卷 9562-9569页

作者： Zhao, Hui Mi, Jiao Yu, Congcong Ge, Rui Fan, Xuewu Chinese Acad Sci Xian Inst Opt & Precis Mech Space Opt Lab Xian 710019 Shaanxi Peoples R China Univ Chinese Acad Sci Beijing 100049 Peoples R China

Wave-front coding (WFC) is a well-known technique that can be used to extend the depth of field (DOF) of incoherent imaging systems. The phase masks make the optical transfer function drop significantly, and digital restoration must be used to obtain a clear image with a largely extended DOF. According to the existing literature, in order to obtain satisfactory restoration results, the optical modulation transfer function (MTF) at the Nyquist frequency is required to be bigger than 0.1, which has already become a popularly accepted design constraint. However, according to our experimental research reported in this paper, this requirement is overly strict. By assembling one already fabricated WFC lens and another camera having physically higher resolution, the MTF of the newly assembled WFC system used in the experimentation has quite a low response at its Nyquist frequency. The experimental results demonstrate that when the optical MTF value at the Nyquist frequency reaches the minimum value of about 0.05, visually satisfactory restoration results can still be obtained as long as the MTF is optimized to be highly insensitive to defocus and the corresponding SNR of the coded intermediate images goes beyond 20 dB at the same time. The experimental results indicate that the overly strict constraint could be alleviated while designing a WFC system. (C) 2019 Optical Society of America

关键词： Extended depth of field Imaging systems modulation transfer function Optical transfer functions Spatial frequency Wavefront encoding

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modulation transfer function of liquid crystal microlenses and microprisms using double dielectric layer

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APPLIED OPTICS 2018年第1期57卷 18-24页

作者： Sova, Oleksandr Reshetnyak, Victor Galstian, Tigran Univ Laval Dept Phys Genie Phys & Dopt Ctr Opt Photon & Laser Pav Opt Photon 2375 Rue Terrasse Quebec City PQ G1V 0A6 Canada Taras Shevchenko Natl Univ Kyiv Phys Fac Volodymyrska St 64 UA-01601 Kiev Ukraine Lensvector Inc 6203 San Ignacio Ave Suite 110 San Jose CA 95119 USA

We investigate electrically tunable liquid crystal (LC) microlenses and microprisms based on double dielectric optically hidden (DDOH) layers. Comparative theoretical study of the spatial resolution limits in the creation of a spatially modulated electric field by the DDOH layer is conducted. Both the depth of the resulting optical phase modulation and its deviation from the desired wavefront are obtained for sine and sawtooth geometries of the DDOH layer's structure. A comparison is provided with the standard LC reorientation approach using patterned electrodes. (C) 2017 Optical Society of America

关键词： microprism Electric fields Liquid Crystals modulation transfer function Microlenses dielectric layer

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Investigation of speckle imagery spectral estimation challenges for modulation transfer function measurements

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OPTICAL ENGINEERING 2019年第7期58卷

作者： Plummer, Philip J. Barnard, Kenneth J. Marciniak, Michael A. US Air Force Res Lab Sensors Directorate EO IR Targeting & Surveillance Branch Wright Patterson AFB OH 45433 USA US Air Force Inst Technol Dept Engn Phys Wright Patterson AFB OH 45433 USA

Efforts to extend speckle-based focal plane array modulation transfer function measurements beyond the detector Nyquist frequency have unearthed challenging spectral estimation issues. In an attempt to better understand the task of speckle imagery spectral estimation, we explore the nuances of various estimation techniques, making comparisons using both real speckle imagery and simulated data. Parameters and features of the techniques investigated include number of image realizations, the size of image realizations, and applications of windows to speckle imagery spectral estimation. Real-world testing considerations such as laser stability and the challenge of collecting significant numbers of independent image realizations are addressed in the analysis. Results from this research show the advantage increasing the number of realizations has on estimation variance, the robustness of smaller realization segments when battling speckle field imagery spatial nonuniformities, the benefits of windowing image segments with regard to power spectral density estimation accuracy, and the impact that the increasing aperture area has on system signal-to-noise ratio. (C) 2019 Society of Photo-Optical Instrumentation Engineers (SPIE)

关键词： power spectral density laser speckle focal plane array modulation transfer function

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modulation transfer function of a fish-eye lens based on the sixth-order wave aberration theory

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APPLIED OPTICS 2018年第2期57卷 314-321页

作者： Jia, Han Lu, Lijun Cao, Yiqing Shanghai Univ Dept Precis Mech Engn Shanghai 200072 Peoples R China

A calculation program of the modulation transfer function (MTF) of a fish-eye lens is developed with the autocorrelation method, in which the sixth-order wave aberration theory of ultra-wide-angle optical systems is used to simulate the wave aberration distribution at the exit pupil of the optical systems. The autocorrelation integral is processed with the Gauss - Legendre integral, and the magnification chromatic aberration is discussed to calculate polychromatic MTF. The MTF calculation results of a given example are then compared with those previously obtained based on the fourth-order wave aberration theory of plane-symmetrical optical systems and with those from the Zemax program. The study shows that MTF based on the sixth-order wave aberration theory has satisfactory calculation accuracy even for a fish-eye lens with a large acceptance aperture. And the impacts of different types of aberrations on the MTF of a fish-eye lens are analyzed. Finally, we apply the self-adaptive and normalized real-coded genetic algorithm and the MTF developed in the paper to optimize the Nikon F/2.8 fish-eye lens;consequently, the optimized system shows better MTF performances than those of the original design. (C) 2018 Optical Society of America

关键词： Genetic algorithms modulation transfer function Numerical analysis Optical elements Optical systems Surface waves

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